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in ponds that contain naturally occurring forage may be significantly more <br />cost efficient than traditional, labor-intensive, raceway or pond fish <br />culture, which rely on the use of artificial feeds. <br />The genetic integrity of wild subpopulations of Colorado squawfish will best <br />be maintained by stocking fish that are progeny of locally captured, wild <br />squawfish. In 1986, FWS began a three-year project to develop techniques <br />for spawning locally caught Colorado squawfish and for rearing their young <br />in gravel-pit ponds. This work is being funded by the Bureau of <br />Reclamation. Previous pond-rearing investigations indicated that growth is <br />variable, depending largely on season of stocking and availability of <br />appropriate-size foods; also, over-winter survival varies greatly among <br />ponds and years, and can be very low. The causes of overwinter mortality <br />are not yet clear, however. Important goals of the current investigations <br />are to identify these mortality factors and to develop ways to lessen this <br />mortality. <br />Methods <br />In May, two rearing ponds were selected and leased from local landowners. <br />These former gravel pits are located between Grand Junction and Fruita, <br />Colorado. Fish Chalet Pond is 1.62 ha and West Pond is 1.34 ha; both have a <br />maximum depth of 3.2 m. West Pond was devoid of fish. Fish Chalet, one of <br />the ponds used during the previous 1983-85 studies, contained common carp <br />(Cyprinus ca io) and channel catfish (Ictalurus punctatus). To eliminate <br />predation by non-native fishes as a potential mortality factor, Fish Chalet <br />Pond was treated with the toxicant rotenone to remove catfish before squaw- <br />fish were stocked. Fathead minnow (Pimephales promelas) populations--a <br />forage base for squawfish--were then established by stocking 175 adult <br />18